KWH delivered vs battery percent expected

[bluevegman]

So I am experiencing from multiple suppliers that the amount of KWH delivered on a charge is more than I would expect if I simply multiply the battery % change vs the size of the battery. Surely if I have a 72.6 battery and want to charge it 50% from 20% to 70% the KWH delivered by the supplier should be 31.3? Or similar for 68.3 usable battery. Thanks

 

[LeoRBK]

The energy input by charger is always more than the energy stored by the battery. There are some losses when charging.

 

[rpannell]

You also need to add the various losses. So add around 15% loss for AC charging and around 5% for DC.

 

[siteguru]

As above - there are losses when charging. My tracker spreadsheet accounts for this - I calculate stored charge (based on %age added x usable battery capacity) and also measure delivered charge (from the wall box app / CCS charger). Below is a snap of all my charges to date and the efficiencies - average is 89.6%:

 

[rpannell]

There are also fixed losses of about 100W consumed by the car whilst charging. This is in addition to the variable losses due to heat in the charging system. 100W on a 50KW DC charger or a 7KW AC charger are insignificant but 100W on a 2KW granny charger is an additional 5% loss.

 

[bluevegman]

Many thanks. This all makes sense. Doesn’t help me do the estimated time to charge vs % needed, but I’ll build the data over time and have a rule of thumb.
Btw. I have a Ubitricity lamppost charger in my street in London. It’s very slow but very cheap. 24p a unit vs 34p at home with Octopus.